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epsilon (ε)

Vertical transverse isotropy thumbnail
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1. n. [Geophysics]

A P-wave parameter for a medium in which the elastic properties exhibit vertical transverse isotropy. Epsilon (ε) is the P-wave anisotropy parameter and equal to half the ratio of the difference between the horizontal and vertical P-wave velocities squared divided by the vertical P-wave velocity squared.

ε ≡ ½ [(C11C33) / C33] = ½ [(VP2VP2) / VP2]

P-wave parameter (ε) for a medium in which the elastic properties exhibit vertical transverse isotropy, where C11 is the horizontal P-wave modulus (perpendicular to the symmetry axis), C33 is the vertical P-wave modulus (parallel to the symmetry axis), VP is the horizontal P-wave velocity and VP is the vertical P-wave velocity.

Reference: Thomsen L: “Weak Elastic Anisotropy,” Geophysics 51, no. 10 (October 1986): 1954–1966.